‘And that is the beginning of this story, that Baldr the good dreamed heavy dreams that his life was in danger. And when he told the Aesir of his dreams, they took counsel together and decided to protect Baldr from all dangers. Then Frigg [Baldr's mother] took oaths from fire and water, iron and all ores, stones and earth, from trees, sicknesses and poisons, also from all four-footed creatures, birds and worms, that they would not harm Baldr. When that had been done and was known to all, the Aesir tarried with Baldr as follows: he placed himself in the midst of their circle and several shot at him, others lifted their axes against him and still others threw stones at him.
And whatever they did he remained unharmed; and all of them thought this to be of great benefit. But when Loki, son of Laufey, saw this, it ill-pleased him that nothing would harm Baldr. Then, in the shape of a woman, he went to Fensal to visit Frigg. Frigg asked this woman whether she knew what the Aesir were doing at their gathering. The woman answered that they were all shooting at Baldr but nothing would harm him. Then Frigg said: Neither weapons nor trees can harm Baldr, for I have taken oaths from them all. Then the woman asked: Has everything sworn this oath to protect Baldr? Frigg replied: West of Valhalla there grows a bush, called mistletoe – it seemed too young to me to ask an oath of it.
Then the woman departed; Loki took the mistletoe, pulled it up and went to the gathering. Hoedr stood furthest outside the circle of men, for he was blind. Then Loki said to him: Why do you not also shoot at Baldr? He replied: Because I cannot see where Baldr stands; and besides, I have no weapon. Then Loki spoke: Do as the others and offer Baldr honour. I will point you in the direction where Baldr stands – shoot at him with this twig. Hoedr took the mistletoe branch and, directed by Loki, shot at Baldr. The shot pierced through Baldr so that he fell to the earth dead, and that was the greatest misfortune that befell men and Gods.’
From: Snorri Sturluson: The Younger Edda, chapter 49